This invention relates to safety apparatus for a mining machine, and more particularly to safety support means for a conveyor of such a machine.
The invention is particularly concerned with, though not limited to, mining machines of the type known as loaders as well as mining machines of the type known as continuous miners. Such machines generally comprise a gathering head for gathering product (e.g., coal) in a mine, a conveyor system extending rearwardly from the gathering head for conveying the product rearwardly for discharge at the rear of the machine, and power generating equipment for driving the conveyor system and gathering head. The conveyor system of the machine comprises an elongate conveyor support or structure pivotally mounted for swinging movement about a horizontal axis extending transversely of the machine between lowered and raised positions, enabling adjustment of the support to different elevations. The machine further comprises a frame having a rear bottom section beneath the support and sides extending upwardly from said section, and hydraulic lift means between said section and the support actuated by the power equipment for pivoting the support. On occasion, it may be necessary to service the hydraulic lift means or certain machine components located in the area between the rear bottom section and the support, which components are generally accessible to service personnel only from the rear between the rear bottom section and the raised support. A significant risk to service personnel working under the support exists in that if hydraulic pressure to the hydraulic lift means for the support is lost, (as may occur during the servicing operations) the support (which can weigh several tons) may swing down under its weight and crush service personnel on the rear bottom section.
While the lift means of the machine may have counter-balance values for retaining the hydraulic fluid therein to prevent the lift means from retracting and to prevent downswing of the support when pressure is lost, such valves have not proven to be completely reliable. Heretofore, reliance has been placed on service personnel propping up the conveyor support with timbers or the like, but in many instances, this has been ignored because of inconvenience in obtaining props and in utilizing them. Moreover, such propping operations themselves involved a substantial risk to service personnel. To install the props, it was necessary for one person to hold each prop in a supporting position while a second person operating the power equipment lowered the conveyor support into engagement with the upper ends of the props. In addition, in its raised supporting position the props were not highly stable in that only the engagement of the upper ends of the props with the conveyor support and the lower ends of the props with the rear bottom section of the frame held the props in position (i.e., there was no means for securing the props in their supporting positions).